1. Field of the Invention
The present invention relates to novel thermoplastic polyimides and a preparation process for these polyimides, aromatic diamines, that is, 1,3-bis(3-aminobenzoyl)benzene and 4,4'-bis(3-aminobenzoyl) biphenyl, which are useful as the raw material for polyimide monomer and other chemicals, and a preparation process for these diamines.
1,3-Bis(3-aminobenzoyl)benzene and 4,4'-bis(3-aminobenzoyl) biphenyl are, utilized, as a raw material for polyimide, polyamide, polyamideimide, bismaleimide and epoxy resin, and can also be used for the curing agent of maleimide compounds and epoxy compounds. The polyimides of the invention prepared by using these aromatic diamines as the raw material monomer are thermoplastic polyimides having excellent processability.
2. Description of the Prior Art
Polyimide resin has acknowledged as a material for heat resistant resin. Polyimide is prepared by reacting a diamine compound with tetracarboxylic acid dianhydride, and has excellent mechanical strength, dimensional stability, flame retardance and electrical inventive properties in addition to the high heat-resistance which is the essential property of the resin. On account of such favorable performance, polyimide has been conventionally used in the field of electric and electronic appliances, space and aeronautic equipment, and transportation machinery. Thus, polyimide has been widely used in the fields where heat resistance is required and is expected to be used in other fields in increasing amounts.
Various kinds of polyimide having excellent properties have been developed in order to meet these demands. For example, a most typical polyimide is an aromatic polyimide; Vespel (Trade mark of E. I. Du Pont de Nemours & Co.) which is obtained by reaction of 4,4'-diaminodiphenyl ether and pyromellitic dianhydride. The polyimide, however, is insoluble and infusible and must be processed by special technique such as sinter molding of powder. Sinter molding is difficult to provide articles having a complex shape and requires finishing operation such as machining in order to obtain satisfactory articles. Thus, sinter molding has a great disadvantage of high processing cost.
Other conventional polyimide resins having excellent properties have no distinct glass transition temperature though excellent in heat resistance, and must be processed by such means as sinter molding in the case of using these resins as molding materials. Other polyimide resins are soluble in solvents such as halogenated hydrocarbons and have disadvantage in solvent resistance, though excellent in processability. Thus previously developed polyimides have both merits and drawbacks in their properties.
New kinds of polyimide which have been improved the above disadvantages or provide a new performance have been disclosed in order to extend the application field of polyimide.
For example, U.S. Pat. No. 4,065,345 and Japanese Laid-Open Patent HEI 2- 018450 have recently disclosed thermoplastic polyimide having recurring units of the following formula (I): ##STR3## for improving the disadvantages of conventional polyimide. The polyimide is expected for wide use as thermoplastic polyimide having a high glass transition temperature and high elastic modulus.
U.S. Pat. No. 4,485,140 has disclosed polyimide having recurring units of the following formula (II): ##STR4## the polyimide has a glass transition temperature of 220.degree. C. and can be melt processable.
However, the polyimide of the latter formula is insufficient in heat resistance, glass transition temperature in particular. The polyimide of the former formula is required to further increase heat-resistance and elastic modulus.
Various methods for improving the diamine component in the raw material monomer have been tried in order to improve properties of polyimide. For example, a polyimide resin having a benzophenone skeleton has been known to have excellent heat-resistance, mechanical properties and adhesive strength. The polyimide resin LARC-TPI which is prepared from 3,3'-diaminobenzophenone has been known to be thermoplastic in addition to having these excellent properties. The resin, however, is still unsatisfactory in processability, although the resin has thermoplastic property.
A method for increasing the molecular chain has recently been employed as a means for enhancing processability.
Known aromatic diamines which can be used for the monomer of polyimide include, for example, 1,3-bis(4-aminobenzoyl)benzene and 1,4-bis[3(or 4)-aminobenzoyl]benzene described in Chemical Abstracts, Vol 80, 82351d; Journal of Chromatography, Vol 119, 569.about.579 (1976); and Journal of Organic Chemistry, Vol 40, No. 8, 1090.about.1094 (1975); and 4,4'-bis(4-aminobenzoyl)biphenyl described in Chemical Abstracts, Vol 111, 214163q; and Mil' to V. 1, Mironov. However, a straight and rigid such as 1,4-bis[3(or 4)-aminobenzoyl]benzene and 4,4'-structure bis(4-aminobenzoyl)biphenyl is still unsatisfactory for improving the processability of polyimide resin. Consequently, development of polyimide resin having further improved processability and aromatic diamine which can be used for preparing such polyimide resin is strongly demanded.